As mentioned above it would be very useful to post the contents of /etc/yum.repos.d/CentOS-Base.repo . Further, you may need to state whether you are connected directly to the internet or you are sitting in a LAN and possibly with a firewall.

By any rate, the basic approach is:1. Make sure that you can browse the internet using the browser, that would ascertain that its not a connection problem. From your post, it doesnt seem to be the connection2. Configure /etc/yum.conf if you are sitting in a LAN to make sure that you get through the proxy, if not in a LAN, dont worry about this step. 3. Configure the /etc/yum.repos.d/*.repo, making sure all the settings are proper.

I will focus on the CentOS-Base.repo, (Note that you also have adobe-linux-i386.repo, you may need to look into it too).This repo has "stanzas", and each specify a particular repository to pull packages from. Following is a basic set up you may find useful:

#additional packages that may be useful[extras]name=CentOS-$releasever - Extrasmirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras#baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

FOR THIS REPO MAKE SURE THE BASEURL IS COMMENTED, IT WORKS JUST FINE

For the other repos make sure of the following:enabled=1gpgcheck=1baseurl=xyz //where xyz is a valid url AND/ORmirrorlist=xyz //giving valid mirror list.